Abstract Research shows that parental involvement and specific parenting practices positively and significantly influence students’ motivation and academic achievement. Conversely, some findings indicate a different relationship in which parental assistance or support negatively correlate with academic performance and motivation. However, the cross-sectional design of many studies makes it difficult to determine whether parental support leads to lower academic achievement or if such a relationship arises because parents are more likely to offer support when their children encounter difficulties at school. This study clarifies the ambiguity by analysing three waves of student data (T1, T2, T3) and two waves of parent data (T1, T3). The data were collected from 420 fourth-grade students and their parents in Portugal across T1, with subsequent data collections for students in T2 (fifth-grade) and T3 (sixth-grade). In addition, we investigate the effects on academic performance and motivation of strategies promoting interest in mathematics and practices emphasising costs. Our results demonstrate distinct effects of parental practices across motivational constructs and mathematics achievement. Among these practices, those promoting interest exhibit the most consistent positive effects between T1 and T3 across all constructs. Supportive parental practices showed a small positive effect on mathematics achievement from T1 to T2, although this effect was weaker than the effect of achievement on support. These longitudinal results clarify previous negative correlations reported in cross-sectional studies by showing that parents tend to increase their support when children are struggling, indicating that parental support reflects a bidirectional and reactive process rather than being inherently detrimental.
Peixoto et al. (2026) studied this question.